I know this can be done with nurbs when construction history is on (little scroll on the status line). You can make a poly surface live to draw on it, but I don't think you can use construction history to modify the curve by altering the poly surface. If anyone knows a way, please explain.

For simplicity:

1. open a new scene
2. create a nurbs sphere
3. modify -> make live
4. use cv curve tool to draw any quick curve shape on the sphere
5. edit curves -> offset -> offset curve with a distance of 0 (or more than 0 for the general idea)
6. move this new curve +5 in y
7. don't delete history
8. make not live
9. select the sphere then go into cv mode (f9) and move some cv's around then notic the offset curve change due to the history
10. once you get your curve in the shape you want, make sure to rebuild it to either 0 to 1 or 0 to #spans.
11. you can also adjust the curve on the surface which will automatically rebuild the offset curve. You will still need to rebuild when you have what you are looking for.

You may lose a little shape when you rebuild but you can usually get back pretty close to your origonal.

I hope that is as clear as mud. pm me if I can help anymore. If you already knew all of that, sorry